swift234

[patternmatch-silgen] Improve silken and diagnostics for switches on bools and tuples of bools.

This patch introduces a new kind of pattern for matching bool literals, i.e. true and false. Essentially, it is very similar to a pattern for matching enum elements, but simpler. Most of the code is just a boiler plate code copy/pasted from the code for enum element patterns. The only different thing is the emitBoolDispatch function, which emits a SIL code for matching bools.

With this patch, we don't get any false non-exhaustive switch diagnostics for switches on bools anymore. And we have a lot of radars complaining about it. For example rdar://16514545 and rdar://20130240.

Note, that this patch fixes the non-exhaustive switch diagnostics without changing the internal representation of bools. Implementing bool as an enum would have the same effect when it comes to these diagnostics and we would get this diagnostics fix for free, i.e. without any code committed here. But implementing bools-as-enums is an ongoing work and I'm investigating its performance implications. If we become confident that bool-as-enum does not have a negative impact on performance and decide to merge it, then we can revert this patch as it would not be necessary anymore. But if we decide to skip the enum-as-bool approach to its performance issues, then we would have at least fixed the false non-exhaustive diagnostics for bools by means of this patch.

Swift SVN r26650